Millions of Americans have little to no money saved for a rainy day.

In fact, according to a survey from community development nonprofit NeighborWorks America, about a third of American adults (more than 72 million people total) don't have any emergency savings. 

When the unexpected occurs, you don't want to be stuck penniless. And while this means you ought to start socking away funds now, keeping an eye on your expenditures can also help beef up your piggy bank. 

Lucky for you, plenty of personal finance tools are free of charge. Here are five of the best resources to help you manage your money:

1. Mint

Mint.com is a free personal financial management service that's now handy on most mobile devices via an app. Once you plug in all your relevant financial information and connect your accounts, you can create personalized budgets based on your income, receive customized tips on how to save money and view easy-to-understand charts and graphs of your expenditures. The Trends feature tracks your spending and net worth over time and Mint Bills, an extension of the original app, sends you bill alerts and allows you to make payments on the go.

2. Personal Capital 

More than 850,0000 people use Personal Capital to track more than $175 billion. Bill Harris, the former CEO of PayPal and Intuit, founded the digital wealth manager in 2009. The service aims to provide an overall picture of how you stand financially, as well as free investment tools that you can access online or on a mobile device. 

3. Level Money

This mobile money meter crunches your data to provide a daily, weekly and monthly "Spendable"--that is, an allotment of cash you're safe to spend. You can also create trackers within the app to keep an eye on your spending habits, whether that's on transportation, food or going out. Level Money aims to act like a financial GPS, getting users to where they are now to where they want to be. 

4. BillGuard 

Protect your well-earned money with the BillGuard app. Aside from tracking your spending like any other personal finance app, BillGuard alerts you of any suspicious activity, ranging from suspicious charges to billing errors to identity theft. You're even notified if you shopped at a merchant at the time that it was hacked. To help you resolve any issues, the app features a card concierge through which you can contact merchants. 

5. Wally

If you prioritize simplicity and design, Wally is the personal finance app for you. Like many of its competitors, Wally tracks your spending, allows you to set budgets and financial goals and provides financial insights. The app also includes a feature called InstaScan, which aims to make it easier for users to update their expenditures. Just take a picture of your receipt and the app does the rest.